Hard Disk Drive High Capacity - GMR head

"In modern disk drives using the IBM innovations of magnetoresistive (MR) or giant magnetoresistive (GMR) heads, the bits are written and read by separate elements in a recording head as it flies over the spinning disk. A writing element writes bits onto the disk and a reading element read the bits by detecting the presence of their faint but tell-tale magnetic fields. The head itself is attached to a slider, an aerodynamically shaped block that allows the head to maintain a consistent flying height above the disk. In turn, the slider is connected to a suspension arm that is controlled by an actuator which can move the head to any track of bits on the disk, from the inner to the outer diameter. Special electronic circuits encode data from the computer's processor prior to writing, and decode the bit pattern after reading. Additional vital electronic circuits keep track of where data is stored on the disk so that it can be readily retrieved when needed, and monitor the motion of the disks and heads so their positions over the disks is always known precisely."

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"As demand for higher areal densities and data rates increases, more sensitive heads are needed
to maintain high quality read-back signals. Newer GMR heads that meet that need are
already being shipped in hard drives. Since GMR technology also uses much of the design,
production and test experience associated with AMR heads, it will evolve more readily and
be shipping in virtually all WD desktop and enterprise drives by the close of 1999.
GMR heads support areal densities greater than 10 gigabits per square inch. Western
Digital’s EIDE desktop hard drives incorporating GMR heads are currently shipping.
The high areal densities attainable with GMR heads enable hard drive
products to offer a maximum storage capacity with a minimum number of components—
i.e., heads and disks. Fewer components mean higher reliability, lower power requirements
and lower storage costs."

"This paper is to analyze effect of the data flex cable and friction in the actuator rotary pivot bearing on performance of head positioning servo systems in micro hard disk drives (HDD). The micro HDD is one of trends in the disk drive industry, which can be used by portable devices such as digital cameras. A nonlinear model of the micro HDD will be established, where its configuration of nonlinearities will be identified with analysis of physical effects and its parameters will be determined with the Monte Carlo method. A control law will be designed to analyze effect of these torque disturbances on performance of head positioning servo systems through simulations and experiments." Kemao Peng; Guoyang Cheng; Chen, B.M.; Lee, T.H. (2003)